Lattice corneal dystrophy type I (LCDI) is an inherited autosomal dominant local amyloidosis, restricted to the corneal stroma. Comparison of electrophoretic profiles of normal and dystrophic corneas revealed a 42 kD protein, which was present only in dystrophic corneas. TheN-terminal sequence of this protein showed identity to transforming growth factor-β induced gene product (βIG-H3). A polyclonal antiserum was raised in chicken against a synthetic peptide identical to theN-terminal portion of βIG-H3. On immunoblots, the antiserum stained the 42 kD band, and also a 68 kD band corresponding to the reported molecular weight of the intact βIG-H3. In normal corneas, only the 68 kD band was present. Immunohistologically, the antiserum stained corneal subepithelial regions, including subepithelial deposits, in dystrophic corneas. In normal corneas, the staining was observed only in the epithelium. These results may reflect the role of βIG-H3 in extracellular matrix construction and/or amyloid formation.